A structure of an LTE system which is an example of a wireless communication system to which the present invention may be applied will be described with reference to FIG. 1.
FIG. 1 illustrates a schematic network structure of an evolved universal mobile telecommunication system (E-UMTS). An E-UMTS system is an evolved version of the UMTS system and basic standardization thereof is in progress under the 3rd Generation Partnership Project (3GPP). The E-UMTS is also referred to as a Long Term Evolution (LTE) system. For details of the technical specifications of the UMTS and E-UMTS, refer to Release 7 and Release 8 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”.
Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), base stations (or eNBs or eNode Bs), and an Access Gateway (AG) which is located at an end of a network (E-UTRAN) and which is connected to an external network. Generally, an eNB can simultaneously transmit multiple data streams for a broadcast service, a multicast service and/or a unicast service.
One or more cells may exist for one BS. The cell provides a downlink or uplink transmission service to several UEs using any one of bandwidths of 1.25, 2.5, 5, 10, 15 and 20 MHz. Different cells may be set to provide different bandwidths. A BS controls data transmission or reception to or from a plurality of UEs. The BS transmits downlink scheduling information to a UE with respect to downlink (DL) data so as to inform the UE of time/frequency domain, coding, data size, Hybrid Automatic Repeat and reQuest (HARQ) associated information of data to be transmitted, or the like. The BS transmits uplink scheduling information to a UE with respect to uplink (UL) data so as to inform the UE of time/frequency domain, coding, data size, HARQ associated information used by the UE, or the like. An interface for transmitting user traffic or control traffic can be used between BSs. A Core Network (CN) may include the AG, a network node for user registration of the UE, or the like. The AG manages mobility of a UE on a Tracking Area (TA) basis. One TA includes a plurality of cells.
Wireless communication technology has been developed to reach the LTE based on Wideband Code Division Multiple Access (WCDMA), but demands and expectations of users and providers have continuously increased. In addition, since other aspects of wireless access technology continue to evolve, new advances are required to remain competitive in the future. There is a need for reduction in cost per bit, service availability increase, the use of a flexible frequency band, a simple structure and an open type interface, appropriate power consumption of a UE, etc.
Recently, 3GPP has been proceeding with standardization of a successor to LTE. In this specification, the successor will be referred to as “LTE-A”. LTE-A is designed to support a wideband covering a maximum frequency of 100 MHz. To this end, a carrier aggregation (CA) technique is employed to achieve wideband using a plurality of frequency blocks. CA uses a plurality of frequency blocks as one large logical frequency band in order to use a wider frequency band. The bandwidth of a frequency block may be defined based on the bandwidth of the system block used in the LTE system. Each frequency block may be referred to as a component carrier (CC) or a cell.
In addition, in the LTE system, a duplex operation of dividing all available resources into DL resources (i.e., resources which a base station uses to transmit a signal to a UE) and UL resources (i.e., resources which the UE uses to transmit a signal to the base station) may be supported. For example, a frequency division duplex (FDD) scheme or a time division duplex (TDD) scheme may be applied. In this way, each resource may be used either for DL or for UL. In the legacy LTE system, use of each resource is specified through system information.
Recently, a method to dynamically designate a DL-UL configuration in performing a duplex operation is under discussion as an improved method for the LTE/LTE-A systems.